Brain and odor: I. Alteration of human EEG by odor administration

Two experiments examined the relationship between time domain patterns of EEG activity and self-reports for individuals exposed to different odorants. In the first experiment, spiced apple, eucalyptus, and lavender odors were evaluated. The three odorants produced consistently different patterns of EEG theta activity and self-reports. These results suggest that odor administration is a reliable variable in manipulating neurophysiological response systems and may be influential in affecting human performance and mood. In order to assess the sensitivity of EEG in the delineation of odor effects, a second experiment was conducted. EEG activity was recorded while subjects smelled five similar commercial odorous chemicals and an unscented base. Subjects completed questionnaires on odor character and mood following each presentation. Results of the experiment indicated little perceptual or mood difference produced by the odors. EEG alpha and theta activity in the left and right hemispheres, however, differed widely depending upon the odor presented and was dissociated from self-report. These results suggest the sensitivity of EEG techniques in odor experiments and indicate that the perceptual component of olfaction accounts for only a limited part of the central nervous system changes produced by smelling an odor.